Current circuit terminal block adapter

ABSTRACT

A terminal block adapter for connecting and disconnecting active current curcuits without danger of open circuiting current devices or loss of continuity to external devices.

United States Patent 11 1 Vandiveer et a1.

[ Jan. 14, 1975 CURRENT CIRCUIT TERMINAL BLOCK ADAPTER [76] Inventors:Paul R. Vandiveer, 312 N. 60th St.; Elbert Wayne Young, 1414 34th St.,Apt. 124, both of Phoenix, Ariz. 85018 [22] Filed: July 20, 1973 21Appl. No.: 381,274

[52] U.S. Cl 339/18 R, 339/19, 339/198,

[51] Int. Cl H01r 9/00, H01r 29/00 [58] Field of Search 339/17-19,339/198, 176, 263, 272, 217, 269; 200/158;

[56] References Cited UNITED STATES PATENTS 2,145,744 1/1939 Whitney339/198 R X 3,146,055 8/1964 Linn 339/198 P X 3,177,457 4/1965 Croghan339/198 P X 3,417,192 12/1968 Elm 339/198 X 3,760,330 9/1973 Bennett eta1..... 339/18 R R1 1,397 1/1894 Sanche 339/269 X Primary ExaminerRoy D.Frazier Assistant Examiner-Terrell P. Lewis Attorney, Agent, orFirm-Cahill, Sutton & Thomas [57] ABSTRACT A terminal block adapter forconnecting and disconnecting active current curcuits without danger ofopen circuiting current devices or loss of continuity to externaldevices.

4 Clainis, 4 Drawing Figures CURRENT CIRCUIT TERMINAL BLOCK ADAPTERsensing elements to current transformers, which appa- The presentinvention relates to terminal blocks, and 7 more particularly, toshunting devices for use in conjunction with current transformers.

In the field of electrical power transmission, means must be provided toreduce the magnitude of current flowing through the power lines. To alevel that can be safely and economically handled by switchboard devicessuch as wattmeters, ammeters and protective relay equipment. By usingcurrent transformers, a relative current can be obtained whose magnitudeis in the range of readily available equipment.

Usually the current transformers, whether driving an instrument or arelay, are permanently affixed to the power lines conveying electricalpower to or from a sub-station. The leads from these currenttransformers are brought to a terminal block on a switchboard panel. Theterminal block permits relatively easy connection or disconnection ofthe relays or instruments and their respective current transformers.

The nature of a current transformer is such that the leads thereof mustalways be in closed circuit. If the leads are open circuited, thevoltage across the secondary winding will rapidly increase, possiblycausing a breakdown of the insulation and destruction of the currenttransformer.

Various terminal blocks and devices have been developed in the past foruse in power sub-stations. U.S. Pat. No. 2,125,256, discloses adetachable terminal board. Spring loaded elements are used to effect anelectrical connection between an existing threaded stud and the post ofthe detachable terminal board. The

.spring loaded electrical contact engaging the threads of the stud, isan unexceptable engineering practice for several reasons. First, thesurface contact between the spring and the ridges of the threads is verysmall. The small surface area will tend to provide a high currentdensity with the attendant danger of burning and corrosion. Secondly,the amount of physical contact is primarily dependent upon the forceexerted by the spring. As the resiliency of the spring will diminishover a period of time and be further degraded by high temperatures, theeffectiveness of the electrical connection will be of a short termduration. U.S. Pat. No. 1,946,889, shows a terminal board having ashunting bar disposed thereacross. A coil spring extends upwardly fromeach of the bus bars of the terminal block generally in verticalalignment with the shorting bar. A connecting pin interconnects theshorting bar with one of the bus bars, whereby a plurality of connectingpins may be used to electrically interconnect two or more of the busbars. Other U.S. Patents generally related to the present inventioninclude, U.S. Pat. Nos. 2,129,524; 2,407,372; 2,756,399; 3,193,794; and3,594,710.

It is therefore a primary object of the present invention to provide aterminal block adapter for current transformers, which adapter permitsthe shorting of the secondary winding of a current transformer prior toconnection or disconnection of a current sensing element.

Another object of the present invention is to provide apparatus useablein conjunction with presently widely used terminal blocks to permit theshorting of two or more bus bars within the terminal block.

Yet another object of the present invention is to provide apparatus forassisting in the connection of current ratusissnnmtibl w thp x ziistin qp Still another object of the present invention is to i'o vide apparatusfor preventing damage to current transformers when current sensingelements are switched from one current transformer source to another.

A further object of the present invention is to provide a low costmodification to existing terminalblocks, which modification permits theshorting of connected current transformers prior to the insertion orremoval of current sensing elements.

A still further object of the present invention is to provide apparatusfor shorting current transformers, which apparatus is adaptable to anyone of the existing presently used terminal blocks.

A yet further object of the present invention is to provide a low costterminal block specially adapted for use with current transformers.

These and other objects of the present invention will become apparent tothose skilled in the art as the description thereof proceeds.

The present invention may be described with more clarity and specificitywith reference to the following drawings, in which:

FIG. 1 illustrates a representative electrical power circuitincorporating the present invention.

FIG. 2 illustrates a cross-sectional view of the present invention.

FIG. 3 illustrates an end view of the present invention.

FIG. 4 illustrates an electrical post useable in conjunction with thepresent invention.

Referring to FIG. 1, there is shown a schematic diagragm of a monitoringcircuit for a three phase power line 1. The power line 1 includes threeindividual lines A, B, and C, which individual lines are representativeof the A, B, and C phases connected in a Y configuration. Currenttransformers are connected to each of the lines, the secondary windingsof each being identified by numerals 2, 3 and 4. The currenttransformers 2, 3, and 4, are directly connected to terminal board 20 atterminals 21, 22, and 23 with the common ground being connected toterminal 24. A second set of terminals 25, 26, 27 and 28 are connectedto terminals 21, 22, 23 and 24, respectively, by bus bars (not shown).

A second terminal board 30 includes a first set of terminals 31-34connected to a second set of terminals 35-38, respectively, by means ofa plurality of bus bars (not shown). Similarly, a third terminal block40 includes a first set of terminals 41-44 connected to a second set ofterminals 45-48, respectively, by means of a plurality of bus bars (notshown).

A relay 5, having terminals 5-1, and 5-2, is connected across terminals25 and 35. Terminal 31 of terminal block 30 is connected to terminal 41of terminal block 40. Another relay 8 having terminals 8-1, and 8-2, isconnected across terminals 45 and 48 of terminal block 40 and is inseries with relay 5. Terminal 48, is connected to the common ground ofcurrent transformers, via terminals 44, 34, 38, 28 and 24. From thisdescription, it may be understood that relays 5 and 8 may be set to beresponsive to a current change within phase A of power lines 1.

Terminal 6-1 of relay 6 is connected to one side of the secondarywinding of current transformer 3 through terminals 26 and 22 of terminalblock 20. Terminal 6-2 is connected to terminal 9-1 of relay 9 throughterminals 36 and 32 in terminal block 30 and terminals 42 and 46 interminal block 40. Terminal 9-2 of relay 9 is connected to the commonground of current transformers through terminals 48 and 44 in terminalblock 40 terminals 34 and 38 in terminal block 30 and terminals 28 and24 in terminal block 20. Again, it may be understood that relays 6 and 9are connected in series and are intended to be responsive to any changein current through phase B of power lines 1.

Terminals 7-1 of relay 7 is connected to one side of the secondarywinding of current transformer 4 through terminals 27 and 23 in terminalblock 20. Terminals 7-2 of relay 7 is connected to terminal -1 of relay10 through terminals 37, and 33 of terminal block 30 and terminals 43and 47 of terminal block 40. Terminal 10-2 of relay 10 is connected tothe common ground of current transformers through terminals 48 and 44 ofterminal'block 40, terminals 34 and 38 of terminal block 30 andterminals 28 and 24 of terminal block 20. Thus, it may be understoodthat relays 7 and 10 are in series and are intended to be responsive toany current change within phase C of power lines 1.

In accordance with good engineering and maintenance practice, the relaysat a sub-station must be periodically removed from the line andmaintained and calibrated to insure their continued reliable operation.Alternatively, the relays may be replaced with ammeters of oth e rcurrent responsive elements. As the power line 1 can not normally bede-energized for such operations, the relays and/or ammeters must bedisconnected from or connected to an energized current transformer. Thenature of current transformers is such that the voltage on the secondarywinding will rapidly rise unless a current path is maintained across thesecondary winding. The rapid voltage rise may cause failure of thesecondary winding insulation resulting in total failure of the currenttransformer. Thus, it is mandatory that a current path be continouslymaintained across the secondary winding of the current transformerthrough a load or by short circuiting the secondary winding.

Referring again to FIG. 1, there is shown an electrical line 11connected to terminal 21 of terminal block 20 and terminal 31 ofterminal block 30. Line 11 shorts out relay 5 thus, relay 5 may beremoved from the circuit after installation of line 11 without anydanger of open circuiting the secondary winding of current transformer2.

As will be described in more detail below, the configuration of theterminals of the terminal blocks of the present invention permits theinsertion or deletion of shorting lines, such as line 11, withoutaffecting the connections of the existing current sensitive devicesplaced across the secondary windings of the current transformers. Oncethe shorting lines have been installed, the current sensitive devicesmay be removed at will without affecting the electrical connections ofthe shorting lines.

Referring to FIG. 2, there is shown a cross-sectional view of terminalblock 20. The terminal block 20 includes a base 49 having a plurality ofwalls 50 extending upwardly therefrom to define a plurality of channels54, which channels are normal to the longitudinal axis of the base. Abus bar 51 is positioned at the bottom of each of these channels and issecured to the base by means of bolts 52 and washers 53. An electricalline may be connected to bus bar 51 by wrapping the electrical lineabout bolt 52 intermediate washer 53 and the bus bar. A good electricalconnection can be effected by tightening bolt 52 to firmly squeeze theelectrical line. A plate 55 may be disposed across each of channels 54and secured to walls 50 by screws 56. The primary purpose of plate 55 isthat of affording a place for noting the phase, voltage or electricalelement connected to the bus bar within the respective channel. Base 49may include relatively thick ends or the ends may be made more robust bythe addition of end plates 57. The latter may be connected to oneanother by means of a bolt 58 extending through base 49.

An insulator bar 60 is secured atop end plates 57 and in generalvertical alignment with one set of terminals of the terminal block. Asshown in FIG. 3, insulator bar 60 is in general vertical alignment withterminals 21. Insulator bar 60 includes a plurality of threadedapertures 61, which apertures positionally conform to channels 54 andare in vertical alignment with a set of terminals (i.e., terminals 21,22, 23 and 24 as shown in FIG. 1).

Referring particularly to FIG. 4 in conjunction with FIGS. 2 and 3, theadjustable terminals 59 of the present invention will be described infurther detail. The adjustable terminal 59 includes a threaded post 63formed of electrically conductive material and including a head 67disposed at the upper end thereof. Lower end 68 may be flattened orconcave to form a good electrical contact with bolt 52. Threaded post 63mates with threaded aperture 62 of insulator board 60 to permitselective electrical contact between bolt 52 and the threaded post. Acap 64 having a threaded stud 65 extending therefrom mates with athreaded cavity 69 within the threaded post. Cap 64 may be ofelectrically non-conductive material and includes a washer 66 disposedat the lower end thereof. Cap 64 may be threaded into or out of threadedpost 63 to position washer 66 toward or away from head 67.

Referring momentarily to the schematic shown in FIG. 1, the operation ofthe adjustable terminal 59 will be described in further detail. It willbe assumed that relay 5 is to be temporarily removed from the line formaintena s p s Line 2-1 of the secondary winding of current transformer2 is connected intermediate washer 53 and bus bar 51 and secured to thebus bar by bolt 52. Threaded post 63 is engaged with threaded aperture62 and turned until it forms a firm electrical contact with the head ofbolt 52. One end of line 11 is wrapped about threaded stud 65 and cap 64is turned until the end of line 11 is securely disposed intermediatewasher 66 and head 67. From this description, it may be understood thatone end of line 11 is electrically connected to the bus bar intermediateterminals 21 and 25 of terminal block 20 without disrupting or openingthe circuit from terminal block 20 to current transformer 2 or toterminal 5-1 of relay 5.

The other end of line 11 is similarly secured to terminal block 30 atterminal 31. For the reasons discussed above, the electrical continuityintermediate terminal 5-2 of relay 5 and terminal 31 of terminal block30 are not affected by the addition of line 11 to terminal 31. Relay 5may now be completely disconnected by removing the line to terminal 25on terminal block 20 and the line to terminal 35 on terminal block 30without opening the current transformer secondary circuit.

The above discussion has been primarily directed to the presentinvention as used in conjunction with the addition or removal of currentsensing elements electrically connected to current transformers. It isto be understood, however, that the terminal block of the presentinvention may be expeditiously used for other purposes and inconjunction with other equipments. In example, the terminal block of thepresent invention may be used to obtain voltage or current readingsacross phases without disrupting any existing circuits. Or, the terminalblock of the present invention may be used for ancillary measuringdevices or power takeoffs.

While the principles of the invention have now been made clear in anillustrative embodiment, there will be immediately obvious to thoseskilled in the art many modifications of structure, arrangement,proportions, the elements, materials, and components, used in thepractice of the invention which are particularly adapted for specificenvironments and operating requirements without departing from thoseprinciples.

We claim:

1. In an electrical power monitoring and test system for electricalpower lines including at least one terminal block for establishingelectrical communication between the monitoring and testing apparatusand the power lines, the terminal block including a plurality ofparallel channels extending transverse to the longitudinal axis of theterminal block, each of the channels having a set of first and a secondelectrical terminals disposed therein and a bus bar disposed within eachchannel for interconnecting each said set of first and second electricalterminals, the improvement comprising:

a. an insulator board extending across the terminal block, saidinsulator board including a plurality of threaded apertures, each ofsaid apertures being in axial alignment with one of said firstelectrical terminals of each said set of terminals;

b. an electrically conducting threaded post threadedly engaging each ofsaid threaded apertures, said post being rotatable into and out ofelectrical contact with the corresponding one of said first electricalterminals; and

c. electrical attachment means for securing an electrical conductor tosaid post; whereby, each of said posts may selectively electricallyengage one of said first electrical terminals of said set of terminalsto provide an electrical pick-off without affecting the electricalintegrity of the electrical circuit connected to the corresponding oneof said set of electrical terminals.

2. The improvement as set forth in claim 1 wherein said insulator boardis rigidly secured to the ends of the terminal block.

3. The improvement as set forth in claim 2 wherein said attachment meanscomprises a. a capped threaded stud;

b. a threaded cavity disposed within said post for re- I ceiving saidstud; and

c. retaining means connected to said stud for securing the electricalconductor to said post.

4. The improvement as set forth in claim 3 including an electricallyinsulated cap secured to said stud; whereby, said stud may be manuallythreaded into and out of said post without danger of electrical shock.

1. In an electrical power monitoring and test system for electricalpower lines including at least one terminal block for establishingelectrical communication between the monitoring and testing apparatusand the power lines, the terminal block including a plurality ofparallel channels extending transverse to the longitudinal axis of theterminal block, each of the channels having a set of first and a secondelectrical terminals disposed therein and a bus bar disposed within eachchannel for interconnecting each said set of first and second electricalterminals, the improvement comprising: a. an insulator board extendingacross the terminal block, said insulator board including a plurality ofthreaded apertures, each of said apertures being in axial alignment withone of said first electrical terminals of each said set of terminals; b.an electrically conducting threaded post threadedly engaging each ofsaid threaded apertures, said post being rotatable into and out ofelectrical contact with the corresponding one of said first electricalterminals; and c. electrical attachment means for securing an electricalconductor to said post; whereby, each of said posts may selectivelyelectrically engage one of said first electrical terminals of said setof terminals to provide an electrical pick-off without affecting theelectrical integrity of the electrical circuit connected to thecorresponding one of said set of electrical terminals.
 2. Theimprovement as set forth in claim 1 wherein said insulator board isrigidly secured to the ends of the terminal block.
 3. The improvement asset forth in claim 2 wherein said attachment means comprises a. a cappedthreaded stud; b. a threaded cavity disposed within said post forreceiving said stud; and c. retaining means connected to said stud forsecuring the electrical conductor to said post.
 4. The improvement asset forth in claim 3 including an electrically insulated cap secured tosaid stud; whereby, said stud may be manually threaded into and out ofsaid post without danger of electrical shock.